Experimental Characterization of Static Behavior of a New GFRP-Metal Space Truss Deployable Bridge: Comparative Case Study

A new glass fiber-reinforced-polymer (GFRP)-metal box-truss composite girder was developed for use in lightweight deployable vehicular bridges with favorable torsional resistance for large spans. This paper describes the experimental characterization of the static behavior of the latest structure characterized by a closed cross section, with a comparative study on an early version having an open cross section. The structural form of the new structure differed considerably from that of the early version. Nondestructive tests with symmetrical and unsymmetrical static loadings were conducted on a newly fabricated prototype to identify the characteristic flexural and torsional performances of the new structure. Additionally, a comparative evaluation of the experimental behavior in terms of load-displacement and load-strain responses was conducted between the new structure and the early version. Favorable results demonstrated that the new structure enabled satisfactory static performances in terms of deployable bridge applications. The resulting comparisons indicated that the new structure featured a flexural resistance identical to that of the early version. However, the addition of lower plane-truss transverse braces in the new design significantly increased the torsional resistance of the space truss system. The overall torsional rigidity of the new structure approximately corresponded to 2.36 times that of the early version. Moreover, the stress state in the extrusion-type GFRP tubular elements of the space truss system was significantly improved. Compared to the early version, the latest structure is more appropriate for use in the primary load-carrying superstructures of large-span deployable bridges under critical unsymmetrical service loading conditions.